The present invention relates to a synthetic fiber capable of absorbing and disabsorbing moisture, entangled and mixed yarn using the same, knitted and woven fabrics using the same, and the transparency of nonwoven fabric using the same.
Synthetic fiber is superior to natural fiber such as cotton in the property of tensile strength, abrasion resistance, dimensional stability, a quick drying, and broadly used in the field of clothing material. However, synthetic fiber does not have the superior moisture absorption as in natural fiber, and by perspiration in wearing, there occur over humidity and tackiness to skin, resulting in poorer comfortable wearing than natural fiber.
On this account a lot of trials in various ways have been carried out to give moisture absorption and water absorption to synthetic fiber. For example, a moisture absorbing fiber, having a value of equal to or more than 2.5% or 1.5%, respectively, in terms of xcex94MR using polyetherester amide as moisture absorbing component, is disclosed in JP-A-9-41204 or JP-A-9-41221. xcex94MR is a difference between moisture content of fiber allowed to stand in the atmosphere of 30xc2x0 C.xc3x9790%RH for 24 hours and moisture content of fiber allowed to stand in the atmosphere of 20xc2x0 C.xc3x9765%RH for 24 hours, defined as a moisture absorbing and disabsorbing coefficient.
xcex94MR is, however, a value which is calculated from moisture contents of the fiber after allowed to stand under different conditions of temperature and humidity for 24 hours. It is practically important for synthetic fiber to absorb or desorb moisture quickly when a condition of temperature and humidity has changed. However, JP-A-9-41204 or JP-A-9-41221 does not give any suggestion about this fact.
On the other hand, JP-A-63-227871, JP-A-63-227872, or the like suggest comfortable materials for apparel with a capability of absorbing and disabsorbing moisture, and also describe the moisture absorbing rate after 15 min. when the material is moved from the circumstance of 20xc2x0 C.xc3x9765%RH to the circumstance of 30xc2x0 C.xc3x9790%RH, and also the moisture disabsorbing rate after 15 min. when the material is moved from the circumstance of 30xc2x0 C.xc3x9790%RH to the circumstance of 20xc2x0 C.xc3x9765%RH. However, the technology mentioned in these document is related to moisture of a absorbing component to a surface of knitted and woven fabrics made of polyester or polyamide fiber by graft polymerization, and results in disadvantages such as harsh touch, and slippy touch, uneven dyeing, a marked reduction in color fastness upon wetting.
Moreover, in general, many of thermoplastic polymers with superior capability of moisture absorption and water absorption are originally colored or have a tendency of gradual coloring with time, resulting in deterioration of quality and grade of fiber goods. For example, a compound fiber with superior moisture absorbing and disabsorbing capability is disclosed in JP-A-8-209450, JP-A-8-311719 or the like. In these documents, modified polyethyleneoxide is used as a component with a moisture absorbing and disabsorbing capability to provide fiber with a superior moisture absorbing and disabsorbing. The documents, however, describe that diisocyanate compounds are used as a modifier for polyethyleneoxide, but they fail to give any suggestion that a change in color tone of fiber materials is successfully controlled. A modified polyethyleneoxide mentioned in examples (a product name: Aquacoke) is modified with aromatic diisocyanate compounds, and the fiber has a problem of gradual change in color tone.
In U.S. Pat. No. 4767825, a nonwoven fabric which is composed of a water absorbing polymer with polyoxymethylene soft segment and hard segment is suggested. This nonwoven fabric, however, is excellent in moisture absorbing and disabsorbing, a property of fiber and fiber-forming, but has a problem of color yellowing or of poor weather-resistance when used long.
A technical subject of the present invention is to provide a synthetic fiber with a superior moisture absorbing and disabsorbing capability, which exhibits a moisture absorption or desorption function according to the condition of temperature and humidity of atmosphere and can exhibit the moisture absorbing and disabsorbing function repeatedly with changes in temperature and humidity, which has less tendency toward a change in color tone, especially yellowing, in storage over a long period of time, which has no problems in touch or dyeability when used as clothing materials; entangled and mixed yarn, knitted and woven fabrics, and nonwoven fabric using the above mentioned synthetic fiber.
The present invention is achieved as a result of having studied zealously to solve above mentioned subjects.
A synthetic fiber capable of absorbing and disabsorbing moisture of the present invention comprising a component capable of absorbing and disabsorbing moisture component and a fiber-forming polymer has a moisture absorption of 1.5% or more when it is allowed to reach a moisture equilibrium under the circumstance of 25xc2x0 C.xc3x9760%RH and then is allowed to stand for 30 min. under the circumstance of 34xc2x0 C.xc3x9790%RH, and has a moisture disabsorption of 2% or more when it is allowed to reach a moisture equilibrium under the circumstance of 34xc2x0 C.xc3x9790%RH and then is allowed to stand for 30 min. under the circumstance of 25xc2x0 C.xc3x9760%RH. The fiber also has a value of xe2x88x921 to 5 in terms of b value in the CIE-LAB color system when it is allowed to stand for 30 days.
In the entangled and mixed yarn of the present invention, the first fiber comprising the above described synthetic fiber capable of absorbing and disabsorbing moisture and the second fiber comprising a polyester fiber are entangled and blended. The above described yarn blend has a mixing weight ratio of (the first fiber)/(the second fiber)=20/80 to 80/20, and the first fiber has a higher boiling water shrinkage than the second fiber.
The knitted and woven fabrics of the present invention is principally constituted by the above mentioned entangled and mixed yarn.
The nonwoven fabric of the present invention is constituted by a synthetic fiber capable of absorbing and disabsorbing moisture having the structure of moisture absorbing and disabsorbing component located in the core and fiber-forming polymer located in the sheath. The above mentioned moisture absorbing and disabsorbing component is a modified polyalkylene oxides obtained as the reaction product of polyalkylene oxides, polyols and aliphatic diisocyanates, and the fiber-forming polymer in the sheath component is obtained from polyamide or polyester.
The modified polyalkylene oxide core component has a weight ratio of 5 to 30 weight % based on the weight of the total fiber. The nonwoven fabric has a designated structure of the bonded structure through the sheath components of the synthetic fiber or of three-dimensional entanglement of the synthetic fiber.
Consequently in the present invention there is provided that a synthetic fiber with a superior moisture absorbing and disabsorbing capability, which exhibits a moisture absorption or desorption function according to the condition of temperature and humidity of atmosphere and can exhibit the moisture absorbing and disabsorbing function repeatedly with changes in temperature and humidity, which has less tendency toward a change in color tone, especially yellowing, in storage over a long period of time, which has no problems in touch or dyeability when used as clothing materials; entangled and mixed yarn, knitted and woven fabrics, and nonwoven fabric using the above mentioned synthetic fiber.
Embodiments
The detailed description of the present invention will be given in the following paragraph.
The synthetic fiber capable of absorbing and disabsorbing moisture of the present invention comprises the moisture absorbing and the disabsorbing component and the fiber-forming polymer. It is necessary that the fiber has a moisture absorption of 1.5% or more when it is allowed to reach a moisture equilibrium under the circumstance of 25xc2x0 C.xc3x9760%RH and then is allowed to stand for 30 min. under the circumstance of 34xc2x0 C.xc3x9790%RH, and has a moisture disabsorption of 2% or more when it is allowed to reach a moisture equilibrium under the circumstance of 34xc2x0 C.xc3x9790%RH and then is allowed to stand for 30 min. under the circumstance of 25xc2x0 C.xc3x9760%RH.
Here the condition of temperature and humidity of 34xc2x0 C.xc3x9790% RH approximately corresponds to the condition of temperature and humidity between human body and clothes when a human wears clothes over the midsummer from early summer. The condition of temperature and humidity of 25xc2x0 C.xc3x9760%RH has been set on the assumption of temperature and humidity condition and indoor environment which is approximately average throughout the year.
Consequently if the fiber has a moisture absorption of 1.5% or more, preferably 2.5% or more, when it is allowed to reach a moisture equilibrium under the circumstance of 25xc2x0 C.xc3x9760%RH and then is allowed to stand for 30 min. under the circumstance of 34xc2x0 C.xc3x9790%RH, the synthetic fiber, when utilized to form clothes, is able to absorb moisture of the vapor perspiration from a human body quickly.
And also it has a moisture disabsorption of 2% or more, preferably 3% or more, when it is allowed to reach a moisture equilibrium under the circumstance of 34xc2x0 C.xc3x9790%RH and then is allowed to stand for 30 min. under the circumstance of 25xc2x0 C.xc3x9760%RH, the synthetic fiber, which once absorbed moisture, is able to desorb quickly the absorbed moisture from the inside space of clothes to the outside space usually having lower temperature and humidity than the ones inside the clothes.
It is difficult to measure actually moisture absorption and desorption separately because in the synthetic fiber the absorption of the vapor perspiration from the human body and the desorption of the same to the outside space of the clothes occur concurrently. Here, however, the moisture absorption and the moisture disabsorption is defined as the index.
It is necessary, as mentioned above, for the synthetic fiber of a the present invention to have moisture absorption of 1.5% or more and moisture disabsorption of 2% or more, and preferably it is desirable that the moisture disabsorption is equal to or more than the absorption. It is because that if the moisture disabsorption is lower than the moisture absorption, the vapor perspiration from the human body is accumulated by degrees with progress of time in the synthetic fiber, and may decrease the moisture absorption of the synthetic fiber. And if the moisture absorption is smaller than 1.5% or if the moisture disabsorption is smaller than 2%, the amount of moisture absorbed or desorbed themselves is small and as a result the inside of the clothes gets over humid.
The above described moisture absorption and desorption are provided by moisture absorbing and disabsorbing component used for synthetic fiber of the present invention. It is desirable for the moisture absorbing and disabsorbing component to have above described moisture absorption and desorption and a low degree of color tone change as described later. Preferably this moisture absorbing and disabsorbing component is a modified polyalkylene oxide obtained as the reaction product of polyalkylene oxides, polyols, and aliphatic diisocyanates. The modified polyalkylene oxide obtained as the reaction product of one or more compounds selected from the group below is the most preferable, because the modified polyalkylene oxide is fiber-forming polymer and, at the same time, can be melt spun. The examples of polyalkylene oxide are polyethylene oxide, polypropylene oxide, and copolymer of both. The examples of polyol are glycols such as ethylene glycol, diethylene glycol and propylene glycol. The examples of aliphatic isocyanate include cycloaliphatic diisocyanate and preferably include dicyclohexylmethane-4,4xe2x80x2-diisocyanate, 1,6-hexamethylene diisocyanate, etc.
Aromatic diisocyanates are not preferable for this usage because they give coloring or yellowing with progress of time.
A modified polyalkylene oxide used in the present invention is obtained as the reaction product of polyalkylene oxides, polyols, and symmetric aliphatic isocyanates. Especially the polyalkylene oxide with weight average molecular weight of 500 to 500,000 is preferably used. If the weight average molecular weight is less than 500, water absorption of a provided modified polyalkylene oxide extremely deteriorates, and at the same time the fiber-forming ability turns bad because of extremely high melt viscosity. On the other hand if the weight average molecular weight exceeds 500,000, obtained modified polyalkylene oxide, when it absorbs water, may be dissolved out from the nonwoven fabric in a form of gel. As the desired examples of the polyalkylene oxide with weight average molecular weight, polyethyleneoxide, polypropyleneoxide, ethyleneoxide/propyleneoxide copolymer and polybutyleneoxide or the mixture of above described polymers are suitable. And among these polyalkylene oxides with weight average molecular weight of 2,000 to 100,000, polyethyleneoxide, polypropyleneoxide and ethyleneoxide/propyleneoxide copolymer are preferably used.
Polyols are organic compounds which have two hydroxyl groups (xe2x80x94OH) in their molecular, and, for example, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentadiol, hexylene glycol, octylene glycol, glycerylmonoacetate, glycerylmonobutylate, 1,6-hexanediol, 1,9-nonanediol, bisphenol-A are suitable, and especially ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol and 1,9-nonanediol are preferably used.
As the symmetric aliphatic diisocyanate compounds reacted with the polyalkylene oxide and polyols are aliphatic isocyanate compounds which have two isocyanate groups in the symmetric position of the molecule, and, for example, dicyclohexylmethane-4,4xe2x80x2-diisocyanate or 1,6-hexamethylenediisocyanate are preferably used.
These modified polyalkylene oxides preferably have melt viscosity of 1,000 to 20,000 poise at 170xc2x0 C. under weight loading of 50 kg/cm2. If the melt viscosity is less than 1,000 poise, the polymer gel is dissolved out of the fiber surface when the fiber absorbs water. And on the other hand if the melt viscosity is more than 20,000, the fiber-forming ability turns poor because of insufficient dispersing ability in polyamide polymer or polyester polymer.
The synthetic fiber of the present invention is required to have a value of xe2x88x921 to 5 in terms of b value in the CIE-LAB color system when it is allowed to stand for 30 days.
This b value is required to have almost no color tone change even in the finished fabric product and not to damage the commercial value, and preferably the b value is 0 to 3.
The b value of synthetic fiber varies according to the impurity of the materials used for fiber-forming polymer, polymeric condition and spinning condition. At present in many cases the main reason of coloring of the polymer results from the moisture absorbing and disabsorbing components used.
Accordingly it is necessary to improve the moisture absorbing and disabsorbing components in order to keep b value within the range mentioned above. In this point the above described modified polyalkylene oxides have exceedingly small coloring rate and is preferably used in the present invention.
The synthetic fiber of the present invention comprises the moisture absorbing and disabsorbing component and the fiber-forming polymer. As the form of the fiber examples as follows are proposed; fiber in which the moisture absorbing and disabsorbing component and the fiber-forming polymer are evenly or unevenly blended, sheath-core type, side-by-side type or island-sea structure type fiber in which the moisture absorbing and disabsorbing component and the fiber-forming polymer are independently located, various types of conjugate fiber such as multi-divided type fiber, in which one component is divided into several parts by the other component, conjugate fiber in which the blend mixture of a moisture absorbing and disabsorbing component and a fiber-forming polymer, as main component, is conjugated with other fiber-forming polymer.
The moisture absorbing and disabsorbing component may be arranged in both inner and/or outer part of the fiber. When the fibers are used in clothing materials, the moisture absorbing and disabsorbing component does not appear on the surface of the fiber and preferably located in the inner (core) part, not to have slippy touch when wet, uneven dyeing or poor color fastness.
The component ratio of the moisture absorbing and disabsorbing component and the fiber-forming polymer in the synthetic fiber may be set to fulfill the above mentioned moisture absorption and desorption simultaneously and, at the same time, it may be set according to the purpose or the end use of the fiber. For example when the above described modified polyalkylene oxide is used it is preferable that the component is within the weight ratio of 5 to 50 weight % on the weight of the fiber. If the content of the modified polyethylene oxide is less than 5 weight %, the desired moisture absorption and desorption may not be obtained, and on the other side if the content is more than 50 weight %, the fiber-forming ability may have some problems which is not preferable.
The examples of the fiber-forming polymer used in the present invention are polyamides such as nylon 6, nylon 66, polyester such as polyethylene terephthalate, polyolefin such as polyethylene and polypropylene and the copolymers of the above mentioned polymers but there is no limitation for the use of polymers. Any additives such as antioxidants, deglossing agents or ultraviolet absorbants may be used.
In addition, it is preferable that the single filament of a synthetic fiber capable of absorbing and disabsorbing moisture generally has fineness of 0.1 to 20 denier, but it is not particularly limited. A cross-section of fiber may have any kind of shape. It is preferable with a respect of cost that a synthetic fiber capable of absorbing and disabsorbing moisture of the present invention is used as continuous fiber of multi-filament, but it can be cut into staple fiber and used as spun yarn.
In the present invention, it is preferable that the synthetic fiber is a crimped textured yarn having crimp. Water absorption of knitted and woven fabrics highly improves by adopting this method when the synthetic fiber was processed into knitted and woven fabrics.
Water absorption of knitted and woven fabrics is classified roughly in two kinds. The first one is the water absorption which is used when water penetrates and spreads into void between knitted and woven fabrics or filaments. The second one is used when fiber itself absorbs water. When the synthetic fiber is given crimp, the void between filaments increases. If the knitted and woven fabrics using crimped yarn touches water, water can penetrate itself quickly into the voids between knitted and woven structure or filaments by capillary action, improving water absorption. This means that the first water absorption increases.
As for the synthetic fiber capable of absorbing and disabsorbing moisture of the present invention, fiber itself has water absorption. This means that the synthetic fiber capable of absorbing and disabsorbing moisture of the present invention has the second water absorption.
In the crimped textured yarn of the present invention, when knitted and woven, yarn or fiber itself has crimp. Therefore when the surface of the knitted and woven fabrics touches water, the water is spread into the voids between knitted and woven structure or filaments by water absorption effects due to crimp, and then the water is absorbed into the inside of the fiber according to the water absorption of the fiber itself. Therefore the crimped textured yarn of the present invention has superior water absorption by a synergistic effect of both water absorption mentioned above, and as a result has as high as or higher water absorption than natural fiber.
Any kind of crimping method can be used, for example false twist method, stuffing crimp method, and jet stuffing by hot jet of heated fluid.
In these methods, false twist method is preferable considering the stable quality and cost. General false twister with pin type or disk type twister can be used. General condition is adopted as false twisting condition. Usually the condition of false twist coefficient 15,000 to 33,000 is adopted. Here false twist coefficient is expressed in product of false twist number (T/m) and square root of fiber denier (d). However, the condition is not limited to these conditions mentioned above so long as effect of the present invention is provided. It is preferable to use two-step heater false twisting in which heat treating is performed in succession in order to control a torque after false twist.
Using this method, an entangled and mixed yarn can be obtained from the synthetic fiber capable of absorbing and disabsorbing moisture of the present invention. In detail in the entangled and mixed yarn of the present invention, the first fiber comprising the above described synthetic fiber capable of absorbing and disabsorbing moisture and the second fiber comprising polyester fiber are entangled. The above described fiber blend has a mixing weight ratio of (the first fiber)/(the second fiber)=20/80 to 80/20, and the first fiber has a higher boiling water shrinkage than the second fiber.
In the entangled and mixed yarn it is necessary that the first fiber is polyamide fiber having moisture absorption, in the condition 34xc2x0 C.xc3x9790%RH, of 1.5 times or more of the one of nylon 6 in order to provide high water absorption and moisture absorption and desorption. If the moisture absorption is less than 1.5 times of nylon 6, desired antistatic property and moisture absorption and desorption are not obtained.
In the first fiber, as the polyamide which is used to include the modified polyethylene oxide, homopolymers of nylon 6, nylon 66, nylon 11, nylon 12, nylon MXD (polymethaxylylene adipoamide) and copolymers of these nylons mentioned above or the mixture are preferably used.
Compound fiber of sheath core type is preferably used as the first fiber. In particular it is desirable for the fiber to have core component of modified polyethylene oxide alone or mixture of modified polyethylene oxide and polyamide, and sheath component of polyamide. When the mixture of modified polyethylene oxide and polyamide is selected, it is possible that both polymers are melt and premixed to get master chip.
The first fiber formed by polyamide series may be manufactured according to conventional method. When the above described sheath core type compound fiber using the modified polyethylene oxide is used as polyamide series fiber, the composition ratio of the core and sheath varies according to the polymer used or to the property required. It is preferable, however, the composition ratio is in the range of 15/85 to 85/15 by weight. If the ratio of the core component is less than this range, entangled and mixed yarn obtained has poor antistatic property or moisture absorption and desorption. On the other hand if the ratio is more than this range, the fiber-forming ability may be damaged which is not preferable.
As polymer component of the second fiber comprising polyester fiber, homopolymers such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate are used. Also copolymers obtained by copolymerizing the above described homopolymers, as a main part, with dicarboxylic acid such as isophthalic acid, 5-sodium sulfo isophthalic acid, naphthalene dicarboxylic acid, and adipic acid or with other glycol component are used. In addition, the mixture of the polyesters is preferably used.
Single filament fineness of polyester fiber constituting the second fiber is not particularly limited. If multifilament yarn with single filament fineness of less than 1.5 d is used, the knitted or woven fabric can obtain peach touch and moreover the water absorption of the fabric is improved.
When the first fiber formed of polyamide fiber and the second fiber formed of polyester fiber are entangled and blended, conventional airjet-texturing technique using airjet nozzle, interlacer and others may be adopted. The number of intermingle which means the degree of entangle or intermingle may have the value within the range of 20 to 120 times/m.
It is necessary for the entangled and mixed yarn to have a mixing weight ratio of (the first fiber)/(the second fiber)=20/80 to 80/20, and preferably within the ratio of 30/70 to 70/30. If the mixing weight ratio is less than 20% of the first fiber, required antistatic property, water absorption, moisture absorption and desorption are not provided. If the mixing weight ratio of the first fiber exceeds 80% of the first fiber, the touch of polyester constituting the second fiber is not provided. And it is difficult to use a high-degree caustic reduction process in caustic treatment which is used in finishing the fabric woven using the yarn blend to manufacture fabrics for blouses and shirts. As a result it is difficult to obtain soft touch. Furthermore, sometimes the pollution to the polyamide series fiber by the disperse dye used for dyeing polyester fiber increases, and as a result color fastness may get poor.
It is necessary for the boiling water shrinkage of polyamide series fiber as the first fiber of an entangled and mixed yarn to be higher than that of polyester fiber as the second fiber.
Boiling water shrinkage here is measured and calculated by the method as follows.
Yarn is wound to make a certain length of hank by hank machine, and then the length of the hank (a) is measured under initial load of 0.1 g/d. After the hank under no load is boiled for 30 min. in boiling water, it is dried. The length (b) of the hank is measured under initial load of 0.1 g/d. Boiling water shrinkage is obtained in the equation as follows.
Boiling water shrinkage(%)=[(axe2x88x92b)/a]xc3x97100
If the boiling water shrinkage of the first fiber of polyamide series fiber is equal to or less than the one of the second fiber of polyester fiber, it is difficult for loops formed by mainly monofilaments of the polyester fiber to appear over the surface of the polyamide series fiber, and consequently, in some case, the touch of the polyester fiber cannot be obtained or the color fastness to light is damaged.
The boiling water shrinkage differential between the polyamide series fiber and the polyester fiber is not particularly limited, but it is preferable that the polyamide series fiber has 3%, preferably 5% higher shrinkage than polyester fiber.
The dry shrinkage of the polyester fiber has a value smaller than polyamide series fiber and has preferably a value of equal to or less than 2%.
The dry shrinkage here is measured and calculated by the method as follows.
The length (I0) of a yarn sample of about 30 cm is measured under load of 0.05 g/d. The yarn is then allowed to stand without any load at 160xc2x0 C. for 30 min. The length (I1) of the yarn is measured under load of 0.05 g/d. The dry shrinkage is obtained in the equation as follows.
Dry shrinkage(%)=[(I0xe2x88x92I1)/I0]xc3x97100
If the dry shrinkage of the polyester fiber has a value of less than the one of the polyamide fiber and less than 2%, especially less than 3%, the bulkiness and peach touch of the knitted and woven fabrics is highly increased.
It is preferable for an entangled and mixed yarn of the present invention that an antistatic property is equal to or less than 1,000V. An antistatic property here is the value that is measured according to following JIS (Japanese Industrial Standards) for the sample which is dyed by conventional method after tube knitted using entangled and mixed yarn of the present invention.
Friction-charged electrostatic potential: JIS L-1094B method.
If the antistatic property of sample is equal to or less than 1,000V, excellent antistatic effect is obtained, and as a result in the dry circumstance as in winter there does not occur hang about or clinging of clothes to body or adhesion of dust caused by static electricity.
It is preferable for an entangled and mixed yarn of the present invention that water absorption is equal to or more than 150%. The water absorption defined here is calculated in the following manner that after the sample, which is allowed to stand in the condition of 25xc2x0 C.xc3x9760%RH for 2 hours, is weighed to get weight of W, and then the weight one minute after absorbing water W60 is obtained according to the method defined by JIS L-1907 5.3. The water absorption R (%) is calculated by the equation as follows.
R(%)=[(W60xe2x88x92W)/W]xc3x97100
If the water absorption is equal to or more than 150%, the perspiration during wearing is preferably absorbed into the clothes quickly.
It is preferable for the entangled and mixed yarn of the present invention to have moisture absorption equal to or more than 1.5%. Moisture absorption here is defined as the differential of the moisture content after standing in the condition of 25xc2x0 C.xc3x9765%RH for 2 hours and the moisture content after standing in the condition of 34xc2x0 C.xc3x9790%RH for 24 hours. If the moisture absorption is equal to or more than 1.5%, the perspiration in vapor during wearing is quickly absorbed into the fiber and over humidity is preferably not recognized.
Knitted and woven fabrics of the present invention are woven or knitted fabric constituted mainly by the entangled and mixed yarn mentioned above. This knitted and woven fabrics may be obtained by using 100% of the entangled and mixed yarn mentioned above, and may be obtained by mixing the entangled and mixed yarn with other yarns by the method of weaving or knitting as long as the property of the present invention is not diminished.
In brief in the entangled and mixed yarn of the present invention, the polyamide series fiber as the first fiber, constituting the entangled and mixed yarn together with the polyester series fiber as the second fiber, contains nylon 4 having high moisture absorption and desorption, or high moisture absorbing and disabsorbing and water absorbing polymer such as polyvinyl pyrrolidone, polyetherester amide and modified polyethyleneoxide. Therefore superior moisture absorption and desorption and a certain degree of water absorption are obtained.
In addition, because an entangled and mixed yarn of the present invention is constituted by the polyester fiber and the polyamide series fiber with higher boiling water shrinkage than the one of polyester fiber, loops and void formed by mainly monofilaments of polyester fiber are forced to appear on the surface of polyamide series fiber by the heat treatment popular in dyeing process. Therefore the entangled and mixed yarn of the present invention can provide high water absorption.
Furthermore, the knitted and woven fabrics containing mainly the entangled and mixed yarn mentioned above can provide the touch of polyester and at the same time can keep the clothes comfortable without any slippy or tacky wet touch, because in wearing the swelled polyamide series fiber absorbing perspiration and moisture does not have contact to the skin.
In addition if the polyester fiber with single filament fineness of equal to or less than 1.5 d and with dry shrinkage value smaller than the one of the polyamide series fiber and of equal to or less than 2% is used as polyester fiber, the knitted and woven fabrics can obtain superior bulkiness and peach touch.
The antistatic property of polyamide series fiber constituting the entangled and mixed yarn of the present invention has friction-charged electrostatic potential of around 2,000V. As compared to general synthetic fiber, it is in the level in which clothes do not cling to skin even if static electricity occurs, but adhesion of dust by static electricity is not prevented. Adhesion of dust does not disappear unless friction-charged electrostatic potential is equal to or less than 1,000V. It is, however, possible to obtain a high grade antistatic property to use polyamide series fiber together with polyester fiber as the entangled and mixed yarn of the present invention. The reason is not clear, but the present inventors understand as follows.
Considering triboelectric series of polyamide and polyester, when polyamide is given static electricity, it has positive charge. On the other hand when polyester is given static electricity it has negative charge. Cotton, silk, rayon, acetate and acrylic fibers are located between the triboelectric series of polyamide and polyester. By the contact with these fibers, polyamide once has positive charge and polyester once has negative charge but next these charges deny each other and as a result total quantity of charging becomes low. In this case a quantity of denied charge varies depending on the mixing ratio of polyamide series fiber and polyester fiber, but excellent antistatic property is provided if the mixing ratio is between the above described range.
Nonwoven fabric of the present invention will be explained in detail next.
As the polyamide adopted as sheath component or a part of the sheath component of the staple fiber constituting the nonwoven fabric, amide polymers such as nylon 4, nylon 6, nylon 46, nylon 66, nylon 11, nylon 12, nylon MXD6 (polymethaxylene adipoamide), polybiscyclohexylmethane decanamide, or the copolymer containing these polymers mentioned above or the mixture of the same are adopted. In addition, as acid component of polyester, aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid and aliphatic dicarboxylic acid such as adipic acid and sebacic acid or esters from these acids mentioned above are proposed. As glycol component, diols such as ethylene glycol, dietylene glycol, 1,4-butanediol, neopentyl glycol, cyclohexane-1,4-dimethanol are proposed. Ester polymers or copolymers obtained from these components are also used. And paraoxybenzoic acid, 5-sodiumsulfoisophthalic acid, polyalkylene glycol, pentaerythritol and bisphenol A may be added or coplymerized to the ester series polymers mentioned above.
Above described modified polyalkylene oxides are adopted in the present invention.
In nonwoven fabric of the present invention, it is preferable for the staple fiber constituting the nonwoven fabric to have weight ratio of modified polyalkylene oxide of core component of 5 to 30% of fiber weight. If this weight ratio is less than 5%, moisture absorption and desorption of staple fiber, namely of nonwoven fabric, deteriorates. On the other hand, if this ratio exceeds 30%, the moisture absorption and desorption is excellent, but the tendency of decreasing of tensile strength of staple fiber, namely of nonwoven fabric, is observed.
In the nonwoven fabric of the present invention the composition ratio of the sheath and core (sheath/core composition ratio) has the value of sheath/core(by weight)=95/5 to 70/30 when the core component is composed of only modified polyalkylene oxide. And when sheath component is composed of the mixture of modified polyalkylene oxide and polyamide or polyester, the composition ratio does not have limitation especially. It is, however, preferable that the composition ratio has the value of sheath/core(by weight)=60/40 to 40/60 considering fiber-forming ability and the moisture absorption and desorption of the staple fiber, namely nonwoven fabric. If the value of the composition ratio is more than the above described range, the moisture absorption and desorption of the staple fiber turns good but the fiber-forming ability turns poor, moreover tensile strength of staple fiber, namely of the nonwoven fabric deteriorates, and as a result even cross-section of the single filament cannot be obtained. On the other hand if compound ratio of core component is smaller than above range, the fiber has excessive thickness of the sheath component and the moisture absorption and desorption of staple fiber deteriorates with excessive polyamide or polyester dispersing in the modified polyalkylene oxides of core component.
It is necessary in the nonwoven fabric of the present invention that the above described staple fiber substantially has core sheath type composition. Core component gives moisture absorption and desorption to staple fiber, and therefore nonwoven fabric has moisture absorption and desorption. In addition, sheath component gives a fiber-forming ability and tensile strength to staple fiber, and therefore strength of nonwoven fabric is improved.
This staple fiber may have a multicore type sheath core structure as well as conventional sheath core structure. In addition, the form of the cross-section of the staple fiber is not particularly limited if the staple fiber has sheath core type section substantially. A cross-section may be selected from the section adopted in general fiber such as multi-leaves, oval or others as well as usual circular section. These polymers may be melted and premixed to get master chip or dry blended.
In the nonwoven fabric of the present invention, it is possible, if necessary, to mix the core component of the sheath core type staple fiber with water absorbing polymers such as sodium polyacrylate, poly-N-vinylpyrrolidone, poly(metha)acrylic acid or the copolymer of the above described polymers and polyvinylalcohol within the range of providing the effect of the present invention.
In addition, it is also possible to use mix the core component and/or sheath component of the sheath core type staple fiber, if necessary, with several additives such as deglossing agents, colorants, flame retardants, deodorants, Light proof agents, heat resistant reagents and anti oxidants within the range of providing the effect of the present invention.
In particular, it is preferable to use benzotriazole type Light proof agents in the sheath component and to use phenol type antioxidants in the core component in order to improve heat resistance and light fastness. As benzotriazole type Light proof agent 2-(2-hydroxy-3,5-di-t-amylphenyl)benzotriazole (xe2x80x9cSeesorb704xe2x80x9d Shipuro Kasei Kaisha LTD.), as phenol type antioxidant 2-t-pentyl-6-(3,5-di-t-pentyl-2-hydroxybenzyl)-4-t-petylphenylacrylate (xe2x80x9cSumilizer GSxe2x80x9d Sumitomo Chemical Co., LTD.) are preferably used.
In the nonwoven fabric of the present invention the nonwoven structure is maintained, for example, by the heated and pressed adhesion between each component fiber in the partially heated and pressed adhesion area, and by the point welding based on thermal adhesion treatment between each of the component fiber by heat treatment in the oven or in other devices. That is, the structure is maintained by the adhesion via the sheath component of the sheath core type fiber.
The partially heated and pressed adhesion is obtained, for example, by pressing the material between heated embossing roll and smooth faced metal roll. The fiber contacted to the embossing pattern on the embossing roll is melted and adhered together and dotted melted area is formed. Mechanical characteristic such as form retention and dimensional stability and tensile strength is given to the nonwoven fabric by this partially heated and pressed adhesion.
In addition, a conventionally known method is adopted as a method to have point welding of component fiber together by thermal adhesion treatment. Hot air circulating type dryer, hot air flow through dryer, suction drum dryer and yankee drum dryer are used as heat treating device. The heat treating temperature and period is selected properly according to the melting point of the sheath component of the fiber. In addition, kneedling processing may be adopted before heat treatment.
When this kind of thermal adhesion treatment is used to get nonwoven fabric, it is acceptable to add binder fiber with low melting point to the component fiber. In this case the material of binder fiber is not particularly limited. As for the polymer constituting binder fiber, however, the polymer with good solubility with sheath component of compound fiber and with melting point lower more than 5 degrees than sheath component polymer is preferable.
In addition, nonwoven fabric of the present invention maintains shape as nonwoven fabric by three-dimensional entanglement between component fibers. For example, this three-dimensional entanglement between component fibers is formed by giving jet of high pressure liquid to the web. This three-dimensional entanglement provides the nonwoven fabric with form retention property, practically enough tensile strength and flexibility.
The nonwoven fabric of the present invention can be manufactured efficiently according to the method mentioned below.
After polyamide or polyester constituting sheath component of staple fiber, and above described polymer constituting core component, namely a modified polyalkylene oxide or mixture of this modified polyalkylene oxide and polyamide or polyester are separately melted, the melted polymers are spun out using a known combined type nozzle. After the melt spun filaments are cooled by the known cooling device and oiled, the filaments are taken up, by roll to obtain undrawn yarn. Once the yarn is taken up, it is drawn without being wound up. And a drawn yarn thus obtained is given mechanical crimp using crimping device as stuffing box, and then cut into predetermined length to give staple fiber.
As drawing process one-step or multi-step drawing machine in the non-heated or heated condition is used. The drawing ratio or drawing temperature in the step of drawing the undrawn yarn may be selected appropriately according to the adopted polymer type or the amount of modified polyalkylene oxide used as the core component.
The number of crimps of the mechanical crimp is 8 to 35/25 mm, preferably 10 to 30 times/25 mm. If the number of crimp is less than 8/25 mm, un-opened parts are easily obtained in the next carding process. On the other hand if the number of crimps is more than 35/25 mm neps are easily obtained.
It is preferable that a percentage of crimp is equal to or more than 5.0%. A cohesiveness of fiber turns bad in the next carding process if a percentage of crimp is less than 5.0%, and as a result uneven density is easily obtained in the web.
Subsequently this staple fiber is carded using carding machines, and carded web is obtained. The staple fiber nonwoven fabric of the present invention is obtained by giving partially heated and pressed adhesion to the provided carded web to have heated and pressed adhesion of component fiber, by giving heat treatment in an oven or by giving high pressure liquid treatment to have three-dimensionally entangled component fibers.
The fiber in the carded web may be arranged according to any method selected from the method as the parallel fiber web with component fiber arranged in a machine direction of the carding machine, the random fiber web with component fiber arranged at random or the semi random fiber web in which component fiber is arranged in the intermediate of both.
Raw fiber, in other words, the component fiber of nonwoven fabric of the present invention, used in manufacturing of the web may contain at least a certain predetermined amount of the staple fiber mentioned above. Accordingly the staple fiber may be used alone or mixed with other staple fibers.
When the web is treated in the process giving partially heated and pressed adhesion, heated embossing roll and smooth faced metal roll are used and the fiber contacted with the embossing pattern on the embossing roll is melted and adhered to form dotted melted area.
This partially heated and pressed adhesion spot has specified area in the surface of the web, and it is not necessary for individual pressed adhered spot to be always circular. The spot preferably has area of 0.1 to 1.0 mm2, and location density, in other words, the pressed adhered spot density has a value of 2 to 80 spots/cm2, more preferably 4 to 60 spots/cm2. If the pressed adhered spot density is less than 2 spots/cm2, the mechanical properties of the nonwoven fabric obtained by heated and pressed adhesion treatment such as form retention property, tensile strength or dimensional stability are not increased. On the other hand if the density exceeds 80 points/cm2, the flexibility and bulkiness of the nonwoven fabric is decreased. The heated and pressed adhesion area ratio defined as the ratio of all the heated and pressed area for all surface area of a web has a value of 2 to 30%, preferably 4 to 20%. If the above described ratio is less than 2%, the mechanical properties of the nonwoven fabric obtained by heated and pressed adhesion treatment such as form retention property, tensile strength or dimensional stability are not increased. On the other hand if the above described ratio exceeds 30%, the flexibility and bulkiness of the nonwoven fabric is decreased.
When the component fibers are three-dimensionally entangled by high pressure liquid treatment, a known method can be used.
For example, there is a method in which the apparatus with array of plurality of jet nozzles having diameter of 0.05 to 1.0 mm, especially of 0.1-0.4 mm, is used. The method gives jet of high pressure liquid of injection pressure 40-100 kg /m2G from the nozzle mentioned above. Nozzles are arranged in rows in an orthogonal direction of progress direction of a web. This treatment by jet may be given to one side or both sides of the web. In the one side treatment if the jet nozzles are arrayed in plurality of lines and the jet pressure is set low at the first step and high at the following step, nonwoven fabric with even and dense entanglement and even formation are obtained.
It is general to use water in normal or raised temperature as high pressure liquid. The distance between nozzle and web is preferably 1 to 15 cm. If this distance is less than 1 cm, the disordered formation of a web is undesirably obtained, and on the other hand when this distance considerably exceeds 15 cm, impact strength of liquid stream colliding with a web is decreased, resulting in poor three-dimensional entanglement of fibers. This high pressure liquid treatment may be adopted in continuous method or in separated method.
When excessive amount of water is removed from the web after the high pressure liquid treatment, any known method may be used. For example, the residual water is removed using squeezer such as mangle roll, and then the web is dried by drying means such as hot air dryer.